IIT JEE , AIEEE Forum - Physics , Magnetism

karthik2007

A long wire is bent to form a plane angle @... find the magnetic field at a point on the perpendicular bisector at a distance x from the vertex. I am not getting the HCV book answer.

Moreover, why is the magnetic field inside a hollow tube zero? Any concrete logical explanation?

elastiboysai

is da ans

(1+sin

/2)I/2pi

elastiboysai

well as for ur second question i'd say its a consequence of ampere's circuital law

consider a circular loop wthin the tube passin thru the point were field is reqd.

_{[ ]}

^{[ ]} B.dl= mu *i enclosd which is zero as no i is enclosd

karthik2007

Yeah got it... thanks elasu

elastiboysai

is da ans 4 magn field correct.

i feel i made a small mistake

karthik2007

no.. thats wrong

elastiboysai

well dude i got ma mistake

heres da right soln

let dist of the pt be d from both da lines

B at the reqd pt say O ,

i hav written down B due 2 1 wire (its not clear in ma pic)

karthik2007

you have considered it to be a finite wire... hmm... I took the qn as to find the magnetic field due to the long wire at the required point... as it;'ll remain long even after bending

elastiboysai

no dude its like u r bendin a single infinitely long wire at a point

itll give 2 divergent wires starting frm a point

karthik2007

yea... i get that but how have u considered the wire to be finite here/

elastiboysai

wat do u mean i have considered the wire to be finite?

in the formula basically the angles

1 and

2are the angles subtended by the endpts of the wire on the pt where field is reqd. here as one end is infin. and another finite. theta 1 is 90 and the other angles is 90- theta /.

if u still think ma soln is wrong nudge me

karthik2007

nono sorry... I made a mistake... I got the answer :)

tarinbansal

I am answering ur second doubt.

In the figure, I hav shown crosssection of a hollow wire carrying current outside the plane of screen(towards U). Consider the current as infinite no of very long current carrying wires. Hence each wire will hav its own mag field which I hav shown for 3 such wires in my firgure. U can see that none of them enters the hollow wire and hene field inside a hollow wire is zero.

Hope U got it.

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